Castsequence, same spell, different conditions

Take a look at this thread.

Brings up reticle on key press, fires @cursor on key release.
https://us.forums.blizzard.com/en/wow/t/on-release-macro/813974

If you would prefer two separate buttons, do this:

Macro 1

#showtooltip
/use Ground Target Spell

Macro 2

#showtooltip
/stopspelltarget
/use [@cursor]Ground Target Spell